Ask HN: Why aren't there partial static generators?

I stumbled upon these old comments: https://news.ycombinator.com/item?id=896744

I was wondering why there aren't partial static generators where everything from blog names, subtitles, author, articles, about page, contact page, and anything else that is not changed often can be made static, but sections such as comments, and possibly often updated galleries remain dynamic.

I personally haven't seen anything like this(or at least I don't think I have). Does anything like this exist? If not, is there a reason why it doesn't?